The present invention is an improvement over the cooling system for machine tools of the type disclosed in U.S. Pat. No. 3,467,177. The cooling system disclosed in U.S. Pat. No. 3,467,177 discloses a cooling fan integrated into the main drive motor for the machine tool head in the form of a milling machine. In this arrangement the air path for the cooling air is defined to cause the ambient cooling air to be drawn into the machine and to travel in close association with the heat generating power transmission elements and the drive motor associated therewith. In traversing this relatively long path the cooling air also travels alongside the drive motor prior to the heated air being exhausted to the atmosphere. Because of the long air flow path the overall cooling effect of the air is reduced. The effectiveness of the cooling air is dependent also on the speed of the drive motor. If the spindle of such a machine tool is operated approximately thirty minutes at 3,000 R.P.M. the increase in temperature of the housing will be 27.degree. Centigrade, if an ambient temperatue of 18.degree. Centrigrade is subtracted therefrom. The ability of such a prior art system to cool the heat generating elements of a machine tool will vary if a variable speed drive motor is utilized and the drive speeds are changed. At the lower drive speeds the cooling ability of this prior art technique may be inadequate. Accordingly, there is a need at the present time for an improved cooling system for machine tools having heat generating elements therein when operating on a workpiece.